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Floodplain Construction Requirements

Always call the City of Portland at 503-823-6892 before you build on, alter, regrade or fill on your property, or if you see building or filling without a City permit sign posted. A permit is required to ensure that projects do not cause problems on other properties and meet city, state and federal requirements.

New buildings in the floodplain must be protected from flood damage. Portland’s building code requires that new residential buildings must be elevated at least two feet above the base, or 100-year, flood except in the Columbia River floodplain where the requirement is one foot above base flood elevation. No new construction or filling is allowed in the floodway, unless it can be demonstrated through hydrologic analysis that it will not increase in the base flood elevation.